1. Field of the Invention
The present invention relates to a coating and developing apparatus, a coating and developing method, and a storage medium.
2. Description of the Related Art
In a photolithography process that is one of semiconductor manufacturing processes, a resist is applied to the front surface of a semiconductor wafer (hereinafter, referred to as a “wafer”), the resist is exposed into a predetermined pattern and then developed, thereby forming a resist pattern. Such treatments are usually performed generally using a system in which an aligner is connected to a coating and developing apparatus performing coating and development of the resist.
Recently, to form a fine resist pattern, liquid-immersion exposure is sometime performed in the aligner. To briefly describe, the liquid-immersion exposure is an exposure method of repeating operations of forming a solution film 12 composed of, for example, pure water between an exposure lens 11 of an exposure device 10 and a wafer W as shown in FIG. 16A, moving the exposure device 10 in a lateral direction as shown in FIG. 16B so that the exposure device 10 is located at a position corresponding to a next transfer region (shot region) 11A, and applying light, to thereby transfer a predetermined circuit pattern to a resist film 14. Numerals 13A and 13B in the drawings respectively denote a solution supply path and a drainage path for forming the solution film 12. Further; in FIG. 16B, the transfer region 11A is illustrated larger than the real size.
A side end surface of the wafer W and upper and lower inclined surfaces adjacent to the side end surface are called a bevel portion, and the pure water constituting the solution film 12 can adhere to the bevel portion and run from the bevel portion to a rear surface of the wafer W during the liquid-immersion exposure. The liquid adhered to the bevel portion that is the side surface portion of the wafer W and run to a peripheral edge portion on the rear surface side becomes dried into particles and can contaminate the wafer W. Hence, a gas containing, for example, HMDS (hexamethyldisilazane) is supplied, before a resist is applied to the wafer W, to the front surface and the bevel portion of the wafer W to perform water repellent treatment (hydrophobic treatment) so as to prevent the pure water from adhering to the bevel portion and running from the bevel portion to the rear surface of the wafer W.
Incidentally, use of a technique called double patterning is being discussed in order to make the line width of the resist pattern finer. To briefly describe the procedure of the double patterning referring to FIG. 17 that is a flowchart showing an example thereof, the already-described water repellent treatment on the front surface and the bevel portion of the wafer W, a resist coating treatment for the first time, a heat treatment (PAB treatment) for removing a solvent component in the resist, a cleaning treatment on the wafer W before exposure, an exposure processing for the first time, a heat treatment (PEB treatment, but not shown) for accelerating a chemical reaction after exposure, and a developing treatment for the first time are performed in this order to form a resist pattern 15 composed of recessed portions 15a and projecting portions 15b as shown in FIG. 18A. After the development, a heat treatment (post-baking treatment) for removing water due to the developing treatment is performed.
Thereafter, a resist coating treatment for the second time is performed to form a new resist film 17, and a heat treatment and a pre-exposure cleaning treatment are performed in order, and exposure processing for the second time is performed to expose the wafer W such that the exposure region is shifted from that of the exposure processing for the first time. Thereafter, a developing treatment for the second time is performed to form a resist pattern 16 as shown in FIG. 18B, and a heat treatment is performed. The wafer W is then carried to an etching apparatus and is etched using the resist pattern 16 as a mask. As described above, photolithography is performed twice in the double patterning, in which a resist pattern finer and denser than a resist pattern formed by a single photolithography is formed.
Depending on a semiconductor device, it is demanded to form a resist pattern having a size ratio between a line width L1 of a recessed portion 16a and a line width L2 of a projecting portion 16b constituting the resist pattern 16 being 1:1 as shown in FIG. 18B in a manufacturing process of the semiconductor device. By employing the double patterning, the projecting portion 16b can be formed after the development for the second time, in the recessed portion 15a of the pattern 15 which has been formed after the development for the first time as described above. Therefore, if the aligner has a performance capable of forming a resist pattern having a size ratio between the line width of the recessed portion and the line width of the projecting portion being 3:1, the aligner can form the resist pattern having a ratio of L1:L2=1:1. Accordingly, it is possible to make the pattern having a ratio of L1:L2=1:1 finer without changing the aligner, and the above described technique is therefore particularly advantageous to form a resist pattern having the above-described ratio.
Incidentally, the study of the contact angles before and after a developing treatment on a wafer which had been treated with WADS, as shown in the later-described reference test, revealed that the contact angle after the development decreased as compared to the contact angle before the development, that is, the effect of the water repellent treatment with HMDS decreased due to contact with the developing solution to decrease the water repellency of the wafer W. This causes a concern that when performing the above-described double patterning using the aligner performing the liquid-immersion exposure, the adhesion of the pure water to the bevel portion can be prevented as shown in FIG. 19A because the bevel portion has a high water repellency at the exposure for the first time, but adherence of the pure water to the bevel portion and running of the pure water to the rear surface of the wafer W occur as shown in FIG. 19B because the water repellency of the bevel portion of the wafer W is decreased at the exposure for the second time, thereby causing particles as already described.
For example, Japanese Patent Application Publication Nos. 2005-175079 and 2007-214279, in which the technique of hydrophobizing the peripheral edge portion of the wafer W is described but performance of the above-described double patterning is not described, are insufficient to solve the problem in the double patterning.